Feed-through lug power and energy incorrect in eBus MQTT API

[dcj]

Reported in SpanPanel/span#230 — the lugs-downstream active-power and energy values published via the eBus MQTT/Homie API are incorrect.

Symptoms:

• lugs-downstream/active-power reports whole-panel main relay power instead of feedthrough-only power
• Energy values (imported-energy, exported-energy) are similarly wrong
• Negative power values appear where none should exist (no generation on feedthrough lugs)
• The v1 REST API (/api/v1/panel) reported these correctly

Workaround: Use the v1 REST API feedthroughPowerW and feedthroughEnergy fields until a fix is released.

Fix: Identified and in progress internally. Will be included in a future firmware release.